201 lines
12 KiB
JSON
201 lines
12 KiB
JSON
{
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"dataType": "CVE_RECORD",
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"dataVersion": "5.2",
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"cveMetadata": {
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"cveId": "CVE-2026-89902",
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"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"state": "PUBLISHED",
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"assignerShortName": "Linux",
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"dateReserved": "2026-09-11T19:38:34.774Z",
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"datePublished": "2026-09-16T10:32:01.655Z",
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"dateUpdated": "2026-10-19T08:54:35.100Z"
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},
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"containers": {
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"cna": {
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"providerMetadata": {
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"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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"shortName": "Linux",
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"dateUpdated": "2026-10-19T08:54:35.100Z"
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},
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"descriptions": [
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{
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"lang": "en",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nLoongArch: Avoid preempt count underflow without probe\n\nLoongArch uses break 11 for the breakpoint placed after an instruction\nthat Kprobes executes out of line. Since userspace can issue the same\nbreak instruction, do_bp() can reach kprobe_singlestep_handler() when\nthere is no current probe.\n\nThe handler actually returns false in this case, but it first calls\npreempt_enable_no_resched(). The corresponding preempt_disable() is done\nby kprobe_breakpoint_handler() on a real Kprobe hit, so it has not run\nhere. As a result, an ordinary userspace breakpoint (code 11) underflows\nthe current task's preempt count.\n\nThis also makes in_interrupt() return true until the task schedules. One\nvisible consequence is the socket cgroup attribution: cgroup_sk_alloc()\ntreats the allocation as interrupt context and assigns the socket to the\nroot cgroup. A socket opened from the SIGTRAP handler can then avoid a\nBPF_CGROUP_INET_SOCK_CREATE policy attached to the task's own cgroup.\n\nReturn as soon as kprobe_running() reports no active probe.\n\nThe same check has appeared in [PATCH v10 2/4] of the original LoongArch\nKprobes series, but was dropped before the feature reached mainline."
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}
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],
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"metrics": [
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{
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"cvssV3_1": {
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"version": "3.1",
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"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
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"baseScore": 7.8,
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"baseSeverity": "HIGH"
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},
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"scenarios": [
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{
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"lang": "en",
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"value": "AV:L - An unprivileged LoongArch process reaches do_bp() then kprobe_singlestep_handler() by executing break 11 (BRK_KPROBE_SSTEPBP). That is a local CPU exception path, not a network protocol, adjacent wireless/Bluetooth frame, or physical device interface.\nAC:L - With no kprobe running on the CPU (the normal case), break 11 always takes the unmatched preempt_enable_no_resched() path and underflows preempt_count. The attacker then calls socket() from their own SIGTRAP handler; no race or victim-controlled state is required.\nPR:L - do_bp() applies no capability or credential check before dispatching BRK_KPROBE_SSTEPBP. Any unprivileged local user who can run code can issue the instruction; init-namespace root and user-namespace capabilities are not required.\nUI:N - The attacker executes break 11 in their own process and, for the cgroup bypass, installs their own SIGTRAP handler that creates sockets. No other user must mount a filesystem, open a device, or otherwise cooperate.\nS:U - Preempt-count corruption and the resulting socket cgroup/BPF misattribution stay inside the host kernel's security authority. This is not a KVM/Xen guest-to-host escape or an IOMMU/DMA boundary bypass.\nC:H - cgroup_sk_alloc() treats the underflow as interrupt context and pins the new socket to the root cgroup, so BPF_CGROUP_INET_SOCK_CREATE and later cgroup bind/connect/egress programs on the task's cgroup do not run. In a container or Cilium-style deployment this bypasses network isolation and can expose protected services.\nI:H - Root-cgroup attribution skips the container's cgroup BPF socket and traffic hooks for that socket, fully bypassing that access-control policy, while the unmatched preempt_enable corrupts kernel preempt_count used for interrupt and atomic accounting.\nA:H - The underflow makes in_atomic() true, so the next schedule (default SIGTRAP teardown or any blocking syscall) hits BUG: scheduling while atomic and can panic the host, especially with panic_on_warn. mem_cgroup_sk_alloc() also skips container socket charging, allowing host memory exhaustion."
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}
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]
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}
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],
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"affected": [
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "unaffected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"arch/loongarch/kernel/kprobes.c"
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],
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"versions": [
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{
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"version": "6d4cc40fb5f58147defc6c0e9d86e6232fe31616",
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"lessThan": "ff40e597d5d98c0c45a4d09df8177202fac9520e",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "6d4cc40fb5f58147defc6c0e9d86e6232fe31616",
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"lessThan": "a1cb727fa27c2d9c7859729cd90db7bc0f46957f",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "6d4cc40fb5f58147defc6c0e9d86e6232fe31616",
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"lessThan": "76395109a051b53860faaec96522ef08ae9e8e27",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "6d4cc40fb5f58147defc6c0e9d86e6232fe31616",
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"lessThan": "c4357ebeee63cb8da1446fc936573a34e68b0f71",
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"status": "affected",
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"versionType": "git"
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},
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{
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"version": "6d4cc40fb5f58147defc6c0e9d86e6232fe31616",
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"lessThan": "72ce4b24676e8b3b75376c4c559dd81c1ac52d5a",
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"status": "affected",
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"versionType": "git"
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}
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]
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},
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{
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"product": "Linux",
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"vendor": "Linux",
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"defaultStatus": "affected",
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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"programFiles": [
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"arch/loongarch/kernel/kprobes.c"
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],
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"versions": [
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{
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"version": "6.3",
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"status": "affected"
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},
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{
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"version": "0",
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"lessThan": "6.3",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.6.157",
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"lessThanOrEqual": "6.6.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.12.110",
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"lessThanOrEqual": "6.12.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "6.18.51",
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"lessThanOrEqual": "6.18.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.2.5",
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"lessThanOrEqual": "7.2.*",
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"status": "unaffected",
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"versionType": "semver"
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},
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{
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"version": "7.3",
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"lessThanOrEqual": "*",
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"status": "unaffected",
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"versionType": "original_commit_for_fix"
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}
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]
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}
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],
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"cpeApplicability": [
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{
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"nodes": [
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"operator": "OR",
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"negate": false,
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"cpeMatch": [
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "6.3",
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"versionEndExcluding": "6.6.157"
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},
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{
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"vulnerable": true,
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"versionStartIncluding": "6.3",
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"versionEndExcluding": "7.2.5"
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},
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{
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"vulnerable": true,
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"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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"versionStartIncluding": "6.3",
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"versionEndExcluding": "7.3"
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}
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]
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}
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]
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}
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],
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"references": [
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{
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"url": "https://git.kernel.org/stable/c/ff40e597d5d98c0c45a4d09df8177202fac9520e"
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},
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{
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"url": "https://git.kernel.org/stable/c/a1cb727fa27c2d9c7859729cd90db7bc0f46957f"
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},
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{
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"url": "https://git.kernel.org/stable/c/76395109a051b53860faaec96522ef08ae9e8e27"
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},
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{
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"url": "https://git.kernel.org/stable/c/c4357ebeee63cb8da1446fc936573a34e68b0f71"
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},
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{
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"url": "https://git.kernel.org/stable/c/72ce4b24676e8b3b75376c4c559dd81c1ac52d5a"
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}
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],
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"title": "LoongArch: Avoid preempt count underflow without probe",
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